Altimeter settings
Thread Starter
Joined: Aug 2001
Posts: 62
Likes: 0
From: Liverpool, UK
Altimeter settings
Hello
How long has ATC used the terms "QNH" and "QFE" for altimeter settings, and how long has the UK used millibars for altimeter settings, was those terms used (and millibars) during WWII? I know the USA used inches of mercury and usually does not refer to the Q codes for altimeter settings, just "altimeters", does that mean above field or MSL?
Luke
How long has ATC used the terms "QNH" and "QFE" for altimeter settings, and how long has the UK used millibars for altimeter settings, was those terms used (and millibars) during WWII? I know the USA used inches of mercury and usually does not refer to the Q codes for altimeter settings, just "altimeters", does that mean above field or MSL?
Luke
Joined: Dec 1998
Posts: 125
Likes: 0
From: UK
Hi Luke
I must confess, I don;t know how long ATC has used the Q codes for - a long time though I would imagine. As far as I know, the UK used Q codes and millibars during the war - but I'm perfectly willing to stand corrected on this. Technically - the UK uses hectopascals - one millibar equals one hectopascal. But in practice, most people refer to millibars. Yes the USA use Inches of Mercury, and they issue clearances in feet on the local altimeter setting, based on inches Hg below the transition altitude of 18000 ft. ABove that it's FL's but still based on inches, but they call it 29.92 in HG instead of 1013 millibars/hectopascals.
Hope this helps
SLT
I must confess, I don;t know how long ATC has used the Q codes for - a long time though I would imagine. As far as I know, the UK used Q codes and millibars during the war - but I'm perfectly willing to stand corrected on this. Technically - the UK uses hectopascals - one millibar equals one hectopascal. But in practice, most people refer to millibars. Yes the USA use Inches of Mercury, and they issue clearances in feet on the local altimeter setting, based on inches Hg below the transition altitude of 18000 ft. ABove that it's FL's but still based on inches, but they call it 29.92 in HG instead of 1013 millibars/hectopascals.
Hope this helps
SLT
DT 